Bobbi Kristina is unfazed by grandmother Cissy Houston's alleged criticism of her engagement to her adopted brother Nick Gordon, and is said to be in the process of planning a Las Vegas wedding.

Cissy, 78, recently called the couple's rumored engagement "incestuous" after viewing pictures of her granddaughter affectionately kissing Gordon, but Bobbi Kristina is said to be unfazed by her remarks according to TMZ.

"[Bobbi] can't please everyone, so she is going to please herself by doing what she wants to do for once," a source told TMZ.

The 19-year-old was recently spotted wearing a diamond engagement ring, and the pair is reportedly trying to keep their engagement and wedding plans a secret, particularly since friends and family have become increasingly concerned for Bobbi Kristina's well-being.

Gordon, 22, was taken in by the late Whitney Houston as a baby although the singer never filed legal papers.

He and Bobbi Kristina are not biologically related, though sources say that the pair has always had a brother-sister type relationship, and that their sudden engagement has shocked friends and family.

"Nick proposed to Krissy on March 10, and she said yes! Krissy said Nick is the only person she trusts in the world. They have a very deep connection," a source told Star.

Since Houston's passing on Feb. 11, Bobby Kristina has reportedly been an emotional wreck and Cissy is said to believe that Gordon is simply trying to take advantage of her fragile state in a bid to cash in on her multimillion dollar inheritance.

"[Bobbi's] taking prescription pills and saying things that make her family feel she's suicidal. Nick is getting her at her most vulnerable. If he really loved her, he'd back off the engagement and just be her friend," the source said.

The couple, who is currently living in Houston's $1.2 million Atlanta townhouse, denies that they are more than friends despite being photographed hand in hand and being intimate in recent weeks.